Chemical leak inspection system

ABSTRACT

A method of visually detecting a leak of a chemical emanating from a component includes aiming a passive infrared camera system towards the component; filtering an infrared image with an optical bandpass filter, the infrared image being that of the leak; after the infrared image passes through the lens and optical bandpass filter, receiving the filtered infrared image with an infrared sensor device; electronically processing the filtered infrared image received by the infrared sensor device to provide a visible image representing the filtered infrared image; and visually identifying the leak based on the visible image. The passive infrared camera system includes: a lens; a refrigerated portion including the infrared sensor device and the optical bandpass filter (located along an optical path between the lens and the infrared sensor device). At least part of a pass band for the optical bandpass filter is within an absorption band for the chemical.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/298,862, filed Dec. 10, 2005, entitled “Methods for PerformingInspections and Detecting Chemical Leaks Using an Infrared CameraSystem,” which is a continuation of PCT International Application No.PCT/2004/012946, filed Apr. 26, 2004, entitled “Systems and Methods forPerforming Inspections and Detecting Chemical Leaks Using an InfraredCamera System,” which claims the benefit of U.S. Provisional PatentApplication No. 60/477,994, filed Jun. 11, 2003, entitled “Method ofDetecting Gas Leaks Using and Infrared Camera System,” U.S. ProvisionalPatent Application No. 60/482,070, filed Jun. 23, 2003, entitled “Methodof Detecting Gas Leaks Using and Infrared Camera System,” and U.S.Provisional Patent Application No. 60/540,679, filed Jan. 30, 2004,entitled “Method of Detecting Gas Leaks Using an Infrared CameraSystem,” all of which are incorporated herein by reference in theirentirety for all purposes.

TECHNICAL FIELD

The present invention relates generally to visually detecting andidentifying chemical, gas, and petroleum product leaks using an infrared(IR) camera system.

BACKGROUND

In the oil and gas business, in the petro-chemical industry, inprocessing plants, and for utility companies and utility providers, forexample, often more time and money is spent trying to find leaks thanfixing leaks. One of the biggest challenges is trying to find the leaksusing conventional methods. Many conventional methods can simply miss aleak and not detect it if the detector is not properly positioned overor downwind of the leak. Also, many conventional methods are very timeconsuming and labor intensive, which leads to more expense. Hence, thereis a great need for a faster, more accurate, and less expensive methodof detecting such leaks.

Petroleum products, such as liquid, gas, and liquid/gas forms ofhydrocarbon compounds (e.g., fossil fuels), are often transmitted orchanneled in pipes. The conventional method of surveying lines forpetroleum product leaks or for detecting petroleum product leaks ingeneral is with a FLAME-PACK ionizer detector (also sometimes referredto as a “sniffer” device). Another recently developed system uses anactive infrared system (having a transmitting infrared source and areceiving sensor) for detecting petroleum product fumes. However, suchsystems require that the detector be within the stream or plume of thepetroleum product leak. These tests merely detect the presence ofpetroleum product fumes at or upwind of the detector. They do notprovide a visual image of the leak. Also, these prior testing methodsrequire the detector to be in the immediate proximity of the leak, whichmay be dangerous and/or difficult for the inspector.

Prior infrared systems designed for evaluating rocket fumes, forexample, would provide an unfocused and fuzzy image, in which it wasdifficult to make out background objects. For example, using an infraredcamera that images a broad range of infrared wavelengths (e.g., 3-5microns) typically will not be useful in detecting small leaks. Onesystem uses a variable filter that scans through different bandwidths inan attempt to identify the bandwidth of the strongest intensity (asquantified by the system). The purpose of this system was an attempt toidentify the chemical make-up of a rocket exhaust based on thewavelength at which the intensity was greatest for the rocket plume.However, this system is not designed to provide a focused visual imageto view the rocket exhaust.

Others have attempted to visualize petroleum product leaks usinginfrared cameras using a “warm” filter setup and/or an active infraredcamera system. A warm filter setup is one in which a filter is used tolimit the wavelengths of light that reach the infrared sensor, but thefilter is not in a cooled or refrigerated portion of the camera, if thecamera even has a refrigerated portion. Such systems have not been ableto provide a focused image capable of quickly and easily detecting smallleaks, nor being capable of detecting leaks from a distance (e.g., froma helicopter passing over a line). Other systems are active and requirea laser beam to be projected through the area under inspection in orderto detect the presence of a chemical emanating from a component.However, with such systems, typically the narrow laser beam must crossthe flow stream for the leak to be detected. Hence, a leak may be missedif the laser beam does not cross the path of the leak and such systemsoften are unable to reliably find small leaks. Hence, a need exists fora way to perform a visual inspection to find leaks with reliability andaccuracy, while being faster and more cost effective than existing leaksurvey methods.

The U.S. Environmental Protection Agency (EPA) has proposed rules toallow visual inspections using infrared cameras in performing leakinspection surveys. However, due to the lack of detection abilities andpoor performance demonstrated by other prior and current systems, theEPA had not yet implemented such rules. Thus, even the EPA has beenwaiting for someone to provide a system or way of reliably andaccurately detecting leaks of various sizes.

SUMMARY OF THE INVENTION

The problems and needs outlined above may be addressed by embodiments ofthe present invention. In accordance with one aspect of the presentinvention, a passive infrared camera system adapted to provide a visualimage of a chemical emanating from a component having the chemicaltherein, is provided. The passive infrared camera system includes alens, a refrigerated portion, and a refrigeration system. Therefrigerated portion has therein an infrared sensor device and anoptical bandpass filter. The infrared sensor device is adapted tocapture an infrared image from the lens. The optical bandpass filter islocated along an optical path between the lens and the infrared sensordevice. At least part of a pass band for the optical bandpass filter iswithin an absorption band for the chemical. The refrigeration system isadapted to cool the refrigerated portion of the infrared camera system.

In accordance with another aspect of the present invention, a method ofvisually detecting a leak of a chemical emanating from a component, isprovided. This method includes the following steps described in thisparagraph. The order of the steps may vary, may be sequential, mayoverlap, may be in parallel, and combinations thereof. A passiveinfrared camera system is aimed towards the component. The passiveinfrared camera system includes a lens, a refrigerated portion, and arefrigeration system. The refrigerated portion includes therein aninfrared sensor device and an optical bandpass filter. The opticalbandpass filter is located along an optical path between the lens andthe infrared sensor device. At least part of a pass band for the opticalbandpass filter is within an absorption band for the chemical. Therefrigeration system is adapted to cool the refrigerated portion. Aninfrared image is filtered with the optical bandpass filter. Theinfrared image is that of the leak of the chemical emanating from thecomponent. After the infrared image passes through the lens and opticalbandpass filter, the filtered infrared image of the leak is receivedwith the infrared sensor device. The filtered infrared image received bythe infrared sensor device is electronically processed to provide avisible image representing the filtered infrared image. The leak isvisually identified based on the visible image representing the filteredinfrared image provided by the infrared camera system.

The foregoing has outlined rather broadly features of the presentinvention in order that the detailed description of the invention thatfollows may be better understood. Additional features and advantages ofthe invention will be described hereinafter which form the subject ofthe claims of the invention. It should be appreciated by those skilledin the art that the conception and specific embodiment disclosed may bereadily utilized as a basis for modifying or designing other structuresor processes for carrying out the same purposes of the presentinvention. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the spirit and scope ofthe invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which illustrateexemplary embodiments of the present invention and in which:

FIG. 1 is perspective view of a chemical leak detection system of afirst embodiment;

FIG. 2 is a schematic of the infrared camera system of the chemical leakdetection system of FIG. 1;

FIGS. 3A-3D are absorption graphs for methane;

FIG. 4 is a transmission curve illustrating a pass band of an opticalbandpass filter;

FIG. 5 is an absorption graph for a small set of alkane chemicals withthe pass band of the first embodiment transposed thereon;

FIG. 6 is an absorption graph for a small set of alkene chemicals withthe pass band of the first embodiment transposed thereon;

FIG. 7 is an absorption graph for a small set of aromatic chemicals withthe pass band of the first embodiment transposed thereon;

FIG. 8 is an absorption graph for a small set of alkane chemicals with aschematic representation of a pass band for a second embodimenttransposed thereon;

FIG. 9 is an absorption graph for a small set of alkene chemicals with aschematic representation of a pass band for a third embodimenttransposed thereon;

FIG. 10 is an absorption graph for a small set of aromatic chemicalswith a schematic representation of a pass band for a fourth embodimenttransposed thereon;

FIG. 11 is an absorption graph for methane with a schematicrepresentation of a pass band for a fifth embodiment transposed thereon;

FIG. 12 is an absorption graph for methane with a schematicrepresentation of a pass band for a sixth embodiment transposed thereon;

FIG. 13 is an absorption graph for ethylene with a schematicrepresentation of a pass band for a seventh embodiment transposedthereon;

FIG. 14 is an absorption graph for ethylene with a schematicrepresentation of a pass band for an eighth embodiment transposedthereon;

FIG. 15 is an absorption graph for propylene with a schematicrepresentation of a pass band for a ninth embodiment transposed thereon;

FIG. 16 is an absorption graph for propylene with a schematicrepresentation of a pass band for a tenth embodiment transposed thereon;

FIG. 17 is an absorption graph for 1,3 butadiene with a schematicrepresentation of a pass band for an eleventh embodiment transposedthereon;

FIG. 18 is an absorption graph for 1,3 butadiene with a schematicrepresentation of a pass band for a twelfth embodiment transposedthereon;

FIG. 19 is an absorption graph for sulfur hexafluorine with a schematicrepresentation of a pass band for a thirteenth embodiment transposedthereon;

FIG. 20 is perspective view of a chemical leak detection system of afourteenth embodiment;

FIG. 21 shows an inspector using an embodiment of the present invention;

FIG. 22 illustrates a use of an embodiment of the present invention toinspect multiple yards from a single yard;

FIGS. 23A-31B are example images obtained using an embodiment of thepresent invention;

FIG. 32 is a schematic of a dual camera embodiment of the presentinvention;

FIGS. 33-35 are flowcharts illustrating methods of using a dual cameraembodiment of the present invention;

FIG. 36 is a schematic of another dual camera embodiment of the presentinvention; and

FIGS. 37 and 38 are flowcharts illustrating more methods of using a dualcamera embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

Referring now to the drawings, wherein like reference numbers are usedherein to designate like or similar elements throughout the variousviews, illustrative embodiments of the present invention are shown anddescribed. The figures are not necessarily drawn to scale, and in someinstances the drawings have been exaggerated and/or simplified in placesfor illustrative purposes only. One of ordinary skill in the art willappreciate the many possible applications and variations of the presentinvention based on the following illustrative embodiments of the presentinvention.

FIG. 1 shows a chemical leak inspection system 20 in accordance with afirst embodiment of the present invention. The chemical leak inspectionsystem 20 of the first embodiment includes a passive infrared camerasystem 22. The passive infrared camera system 22 of the first embodimentis adapted to provide a visible image representing a filtered infraredimage of a chemical emanating (e.g., leaking) from a component havingthe chemical therein, as discussed in more detail below.

As shown in FIG. 1, the infrared camera system 22 may be mounted on aframe 24. A shoulder-rest portion 26 and handles 28 may be attached tothe frame 24, as shown in FIG. 1. The shoulder-rest portion 26 and thehandles 28 aid in holding the system 20 during an inspection (see e.g.,FIG. 21 discussed below). Typically during an inspection using thissystem 20, an inspector will walk around various components whilecarrying the system 20 on his shoulder and aiming the system 20 towardthe components to look for leaks. In other embodiments, however, thecamera system 22 may be handled or carried in other ways (e.g., by hand,from a vehicle, on a vehicle, on a tripod, on a gyro-stabilizedplatform, by a harness, etc.). Also, as discussed further below,inspections using an embodiment of the present invention may beperformed from a vehicle (moving and not moving).

The leak inspection system 20 of the first embodiment also has aflat-panel display screen 30 (e.g., LCD display) electrically coupled tothe infrared camera system 22 (see e.g., FIG. 1). The visible images(representing the filtered infrared images) provided by the camerasystem 22 may be displayed on the display screen 30 during aninspection. The system 20 preferably includes a video recording device32 (not shown in FIG. 1, but see, e.g., FIG. 21 discussed below)electrically coupled to the camera system 22 for recording imagesobtained by the camera system 22 during use of the system 20. The videorecording device 32 may be attached to the frame 24 or it may be carriedseparately by the inspector (e.g., in a backpack or in a carrying case34 as shown in FIG. 21), for example. The video recording device 32 mayrecord the images in a digital and/or analog format, for example. Thus,during use of the system 20 for locating a leak, an inspector may find aleak visually, as viewed on the display screen 30, and then recorddetailed and focused images of the leak using the video recording device32 for future observation and/or for obtaining a record of the leak.

The system 20 of the first embodiment has a battery 36 electricallycoupled to the infrared camera system 22. Preferably, the system 20 ispowered by the battery 36 during use of the system 20 to allow theinspector to move about freely during an inspection. In otherembodiments, however, the system 20 may be powered via a power cord byelectricity from a wall outlet, from a generator, or from an alternatorof a vehicle, for example. Typically, it will be less preferable topower the system 20 via a power cord, as it may limit the mobility ofthe inspector and/or slow down the inspection process.

FIG. 2 is a schematic of the infrared camera system 22 of FIG. 1 toillustrate some of the components therein. In the first embodiment, thepassive infrared camera system 22 has one or more lenses 38 in a lensassembly 40 for optically focusing the image. Preferably, the lensassembly 40 is removable to allow for different lens assemblies (e.g.,with different focal ranges) to be removably installed on the camerasystem 22. The camera system 22 has a refrigerated portion 42 thatcomprises therein an infrared sensor device 44 and an optical bandpassfilter 46. The refrigerated portion 42 is preferably defined by aninterior of a Dewar container 48. Preferably, the Dewar container 48 hasan evacuated region 50 surrounding the refrigerated portion 42 toprovide insulation. The Dewar container 48 may be made from metal and ithas at least one Dewar window 52 for allowing the infrared image fromthe lens assembly 40 to enter into the refrigerated portion 42. Theinfrared sensor device 44, located in the refrigerated portion 42, isadapted to capture infrared images that come into the refrigeratedportion 42 via the lens assembly 40. In a preferred embodiment, theinfrared sensor device 44 is a focal plane array (FPA) of IndiumAntimonide (InSb) sensors (e.g., a 320×256 matrix) to provide a highsensitivity in the 3-5 micron range of infrared light, for example.Other materials may be used for the infrared sensor device 44 in otherembodiments to provide high sensitivity to other wavelength ranges ofinfrared light. The infrared sensor device 44 is electrically coupled toother electronic components (represented generally by block 54 in FIG.2), which may be inside and/or outside of the camera system 22. Thedesign of the infrared sensor device 44 and the electronic components 54for the camera system 22 may vary for other embodiments of the presentinvention.

The refrigerated portion 42 is cooled by a refrigeration system 60. Therefrigeration system 60 used may vary for different embodiments of thepresent invention. Preferably, the refrigeration system 60 is capable ofmaintaining the temperature in the refrigerated portion 42 below about100 K (i.e., less than about −173° C.). More preferably, the temperaturein the refrigerated portion 42 is maintained between about 75 K andabout 85 K by the refrigeration system 60. In the first embodiment, therefrigeration system 60 includes a closed-cycle Stirling cryocooler, asillustrated schematically in FIG. 2. The actual configuration of theStirling cycle cryocooler 60 for a given embodiment may vary from thatshown in FIG. 2. A cold finger 62 may be used to provide a thermalcommunication between the refrigerated portion 42 and a regeneratorcylinder 64, as shown in FIG. 2. The Stirling cycle cryocooler 60 mayuse helium as a refrigerant or cryogenic fluid, for example. In apreferred embodiment, a closed-cycle Stirling cryocooler 60 may be usedto thermally stabilize the temperature in the refrigerated portion 42 atabout 77 K, for example. A preferred infrared camera system 22, forexample, for use in an embodiment of the present invention is a Merlin™mid-wavelength infrared (MWIR) high-performance camera available fromIndigo Systems, Inc. in California.

As illustrated schematically in FIG. 2, the optical bandpass filter 46is located along an optical path between the lens assembly 40 and theinfrared sensor device 44, and hence infrared images are filtered by theoptical bandpass filter 46 before reaching the infrared sensor device44. The optical bandpass filter 46 of the first embodiment has a passband (bandpass transmittance range) located between about 3100 nm andabout 3600 nm. Because the optical bandpass filter 46 is cooled, i.e.,located in the refrigerated portion 42, in the first embodiment, thefilter 46 works better than if it were not cooled (e.g., not in therefrigerated portion 42), and it allows for a more focused image than ifa warm (uncooled) optical bandpass filter configuration were used. In apreferred embodiment, the optical bandpass filter 46 is cooled to atemperature below about 100 K. Cooling the optical bandpass filter 46 inthe refrigerated portion 42 (i.e., “cold” filter configuration) providesa greater temperature contrast (greater temperature differential)between the leaking chemical and the optical bandpass filter 46, whichincreases the sensitivity of the camera system 22 for imaging theleaking chemical. Cooling the optical bandpass filter 46 effectivelyreduces the background noise of the filter 46 (as perceived by theinfrared sensor device 44). When the optical bandpass filter 46 is notcooled (i.e., “warm” filter configuration), the level of backgroundnoise produced by the filter itself is much higher (relative to a coldfilter configuration) and thus the sensitivity to detecting the infraredlight absorbed by the leaking chemical after the infrared image passesthrough the warm filter is reduced. Also, in a warm filterconfiguration, the temperature difference between the optical bandpassfilter and the leaking chemical is much smaller than that of a “cold”filter.

The camera system 22 of FIGS. 1 and 2, of the first embodiment, is apassive infrared camera system. Hence, the camera system 22 relies onthe background (whatever the background may be) to be a reflector ofenvironmental light and heat to the camera system 22. Most chemicals ofinterest have one or more absorbance bands (wavelength ranges where theabsorbance of infrared light is orders of magnitude higher). Forexample, FIGS. 3A-3D show absorbance graphs for methane (CH4) gas basedon experimental data.

In each graph of FIGS. 3A-3D, the vertical axis is absorbance (unitless)and the horizontal axis is wavelength (μm) of infrared light.Transmission and absorbance are inversely related. Transmission istypically defined as the fraction of light that reaches a detector afterpassing through a sample (e.g., an optical filter, a gas):T=I/Io or % T=100(I/Io),

where I denotes light intensity reaching the detector after passingthrough a sample, Io denotes light intensity of a reference beam orsource beam with no sample present, T denotes transmission (expressed asa fraction), and % T denotes transmission (expressed as a percentage).Absorbance is a logarithmic scale that increases as transmissiondecreases:A=log 10 (Io/I),

where A denotes absorbance. Infrared radiation is often measured inunits of wavelength (e.g., microns or nanometers). Also, infraredradiation is sometimes measured in units called wavenumbers (cm⁻¹):wavenumber (cm⁻¹)=107/λ=E/hc×1/100,

where λ is wavelength in nanometers, E is energy (J), h is Planck'sconstant (6.626×10⁻³⁴ J·s), and c is the speed of light (3.0×10⁸ m/s).Hence, the wavenumber of a light wave is directly proportional to itswavelength and its energy.

FIG. 3A shows the absorbance of methane from about 1.5 μm to about 16.5μm (infrared light). Note that for methane, there are two majorabsorbance bands 71, 72 where the absorbance of infrared light is muchhigher (orders of magnitude higher) than at other adjacent wavelengths.A first absorbance band 71 is located between about 3.1 μm and about 3.6μm, and a second absorbance band 72 is located between about 7.2 μm andabout 8.2 μm (see FIG. 3A). FIG. 3B shows a range of wavelengths betweenabout 3.15 μm and about 3.45 μm to illustrate the first absorbance band71 of FIG. 3A in more detail. Note that the vertical scale for the graphin FIG. 3A is the same as that of FIG. 3B. FIG. 3C shows a range ofwavelengths between about 7.2 μm and about 8.2 μm to illustrate thesecond absorbance band 72 of FIG. 3A in more detail. Note that thevertical scale of the graph in FIG. 3C is orders of magnitude smallerthan that of FIG. 3A. There are also 1 other absorbance bands (73) formethane in the range shown in FIG. 3A, but they have orders of magnitudeless absorbance than the first and second absorbance bands 71, 72. Forexample, a third absorbance band 73 is shown in FIG. 3A at about 2.3 μm.FIG. 3D shows a range of wavelengths between about 2.15 μm and about2.45 μm to illustrate the third absorbance band 73 in more detail. Thevertical scale for the graph in FIG. 3D is orders of magnitude smallerthan that of FIGS. 3A-3C. Hence, methane has a much higher absorbance ofinfrared light between about 3.1 μm and about 3.5 μm (overlapping orwithin the first absorption band 71). Thus, an infrared camera system 22adapted to detect infrared light between about 3-5 μm, for example, willhave high sensitivity for imaging methane between about 3.1 μm and about3.5 μm. The absorbance of methane at the second absorbance band 72 (seeFIG. 3A) may be easily detected as well by an infrared camera system 22adapted to detect infrared light at that range (e.g., about 7-8 μm).

In a preferred embodiment of the present invention adapted to visuallydetect a certain chemical (and perhaps other chemicals as well) leakingfrom a component, the optical bandpass filter 46 is located in therefrigerated portion 42 of the infrared camera system 22 and the opticalbandpass filter 46 has a pass band that is at least partially located inan absorption band for the chemical. For example, in the firstembodiment, the optical bandpass filter 46 has a pass band 80 locatedbetween 3200 nm and 3550, as illustrated by the transmission curve forthe filter 46 in FIG. 4. The first embodiment is adapted to visuallydetect methane, for example, (as well as other chemicals). As discussedabove, methane has a first absorption band 71 (see FIGS. 3A and 3B)located between about 3100 nm and about 3500 nm.

The optical bandpass filter 46 of the first embodiment has a full widthat half maximum (HW) 82 of about 64.4 nm, a center wavelength 84 ofabout 3382 nm, and a peak transmission 86 of about 91.16%, as shown intransmission curve of FIG. 4. The optical bandpass filter 46 of thefirst embodiment is a single bandpass passive filter formed on a quartz(SiO₂) substrate, which is currently preferred. A preferred bandpassfilter providing such performance characteristics may be obtained fromSpectrogon US, Inc. in New Jersey, for example. Other optical bandpassfilters of other embodiments may have different transmission curves withdifferent pass bands, different shapes, different materials, anddifferent characteristics (e.g., full width at half maximum 82, centerwavelength 84, peak transmission 86, etc.). There are many differentoptical bandpass filters available from numerous manufacturers.Referring to FIG. 4, the optical bandpass filter 46 of the firstembodiment allows a transmittance greater than about 45% for infraredlight between about 3360 nm and about 3400 nm to pass therethrough.Another optical bandpass filter (curve not shown) may be used inalternative, for example, that allows a transmittance greater than about45% for infrared light between about 3350 nm and about 3390 nm to passtherethrough, which may provide similar or essentially the same resultsas the filter of the first embodiment.

FIG. 5 is a graph between 3000 nm and 3600 nm showing absorption bandsfor some common alkane chemicals: methane (71), ethane (88), propane(90), butane (92), and hexane (94), for example. In FIG. 5, the passband 80 for the filter 46 of the first embodiment has been overlaid withthe absorption bands 71, 88, 90, 92, 94. In FIG. 5, note that at leastpart of the pass band 80 for the optical bandpass filter 46 is locatedwithin the first absorption band 71 for methane. The use of this opticalbandpass filter 46 in the first embodiment provides a high sensitivityto infrared light being absorbed by methane between about 3200 nm andabout 3500 nm (see FIG. 5). Also, note that the pass band 80 for thisoptical bandpass filter 46 also provides a high sensitivity to infraredlight being absorbed by ethane (88), propane (90), butane (92), andhexane (94) between about 3200 nm and about 3500 nm (see FIG. 5).Although an embodiment may be adapted to detect a certain chemicalleaking from a component, the same set up may also be useful and capableof detecting a set or group of chemicals, as is the case for the firstembodiment of the present invention. Thus, the infrared camera system 22of the first embodiment is adapted to provide a visible imagerepresenting an infrared image of methane, ethane, propane, butane,and/or hexane emanating from a component.

FIG. 6 is a graph between 3000 nm and 3600 nm showing absorption bandsfor some common alkene chemicals: propylene (96) and ethylene (98), forexample. In FIG. 6 (as in FIG. 5), the pass band 80 for the filter 46 ofthe first embodiment has been overlaid with the absorption bands ofpropylene (96) and ethylene (98) located between 3000 nm and 3600 nm. InFIG. 6, note that at least part of the pass band 80 for the opticalbandpass filter 46 is located within the absorption bands 96, 98 shownfor propylene and ethylene. Thus, the infrared camera system 22 of thefirst embodiment is also adapted to provide a visible image representingan infrared image of propylene and/or ethylene emanating from acomponent.

FIG. 7 is a graph between 3000 nm and 3600 nm showing absorption bandsfor some common aromatic chemicals: o-xylene (100), toluene (102), andbenzene (104), for example. In FIG. 7 (as in FIGS. 5 and 6), the passband 80 for the filter 46 of the first embodiment has been overlaid withthe absorption bands of o-xylene (100), toluene (102), and benzene (104)located between 3000 nm and 3600 nm. In FIG. 7, note that at least partof the pass band 80 for the optical bandpass filter 46 is located withinthe absorption bands 100, 102, 104 shown for o-xylene, toluene, andbenzene. Thus, the infrared camera system 22 of the first embodiment isalso adapted to provide a visible image representing an infrared imageof o-xylene, toluene, and/or benzene emanating from a component.

In other embodiments adapted to visually detect a methane gas leakemanating from a component (and/or some other chemical having anabsorption band overlapping or near that of the first absorption band 71for methane), the optical bandpass filter 46 may have any of a varietyof characteristics, including (but not limited to): the pass band of theoptical bandpass filter having a center wavelength located between about3375 nm and about 3385 nm; the optical bandpass filter being adapted toallow a transmittance greater than about 80% of infrared light betweenabout 3365 nm and about 3395 nm to pass therethrough; the pass band ofthe optical bandpass filter having a center wavelength located betweenabout 3340 nm and about 3440 nm; the pass band of the optical bandpassfilter having a center wavelength between about 3360 nm and about 3380nm; the pass band for the optical bandpass filter being located betweenabout 3100 nm and about 3600 nm; the pass band for the optical bandpassfilter being located between about 3200 nm and about 3500 nm; the passband for the optical bandpass filter being located between about 3300 nmand about 3500 nm; the pass band of the optical bandpass filter having afull width at half maximum transmittance that is less than about 600 nm;the pass band of the optical bandpass filter having a full width at halfmaximum transmittance that is less than about 400 nm; the pass band ofthe optical bandpass filter having a full width at half maximumtransmittance that is less than about 200 nm; the pass band of theoptical bandpass filter having a full width at half maximumtransmittance that is less than about 100 nm; the pass band of theoptical bandpass filter having a full width at half maximumtransmittance that is less than about 80 nm; the optical bandpass filterbeing adapted to allow a transmittance greater than about 70% at thecenter wavelength; the pass band for the optical bandpass filter havinga center wavelength located within the absorbance band for the chemical;the pass band for the optical bandpass filter having a center wavelengthlocated partially outside of the absorbance band for the chemical; andcombinations thereof, for example.

In other embodiments, the optical bandpass filter 46 may comprise two ormore optical filters (e.g., in series) located in the refrigeratedportion 42 (i.e., cooled filters) to provide the same function as onesingle bandpass passive filter. For example, a first optical filter (notshown) of the optical bandpass filter 46 may have a high pass filtercharacteristic to allow infrared light greater than about 3100 nm topass therethrough, and a second optical filter (not shown) of theoptical bandpass filter 46 may have a low pass filter characteristic toallow infrared light less than about 3600 nm to pass therethrough, whichtogether provide an effective pass band located between about 3100 nmand 3600 nm.

An embodiment of the present invention may be adapted to visually detecta leak of any of a wide variety of chemicals (or evaporated gasestherefrom), including (but not limited to): hydrocarbon; methane;ethane; propane; butane; hexane; ethylene; propylene; acetylene;alcohol; ethanol; methanol; xylene; benzene; formaldehyde; 1,2butadiene; 1,3 butadiene; butadiyne; acetone; gasoline; diesel fuel;petroleum; petrochemicals; petroleum by-product; volatile organiccompound; volatile inorganic compound; crude oil products; crude oilby-products; and combinations thereof, for example. FIGS. 8-19illustrate some example absorption bands (among many) for some examplechemicals (among many) that may be detected while leaking from acomponent using an embodiment of the present invention, and some examplepass bands (among many) for the optical bandpass filter 46 that may beused in an embodiment of the present invention.

In FIGS. 8-19, the pass band 80 for the optical bandpass filter 46 isschematically represented by a rectangular box to show its approximateplacement relative to the absorption bands of the chemicals. As is wellknown by those of ordinary skill in the art, the actual pass band for anoptical bandpass filter will typically have some sort of curve shape(often a bell-curve shape) rather than being rectangular. Therectangular shape is merely used for schematic illustration, as theactual pass band (and the actual transmission curve) for an opticalbandpass filter 46 of an embodiment may have any of a wide variety ofshapes (symmetry, asymmetry, height, slope, skew, full width at halfmaximum, peak transmission, etc.).

FIG. 8 shows some absorption bands 71, 88, 90, 92, 94 for the samealkanes from FIG. 5 from 3000 nm to 3600 nm. In FIG. 8, the pass band 80for the optical bandpass filter 46 of a second embodiment is locatedbetween about 3300 nm and about 3400 nm with a full width at halfmaximum less than about 100 nm, for example. FIG. 9 shows someabsorption bands 96, 98 for the same alkenes from FIG. 6 from 3000 nm to3600 nm. In FIG. 9, the pass band 80 for the optical bandpass filter 46of a third embodiment is located between about 3250 nm and about 3510 nmwith a full width at half maximum less than about 250 nm, for example.FIG. 10 shows some absorption bands 100, 102, 104 for the same aromaticsfrom FIG. 7 from 3000 nm to 3600 nm. In FIG. 10, the pass band 80 forthe optical bandpass filter 46 of a fourth embodiment is located betweenabout 3200 nm and about 3580 nm with a full width at half maximum lessthan about 350 nm, for example.

FIG. 11 shows the first absorption band 71 for methane (see e.g., FIG.3A). In FIG. 11, the pass band 80 for the optical bandpass filter 46 ofa fifth embodiment is located between about 3200 nm and about 3350 nmwith a full width at half maximum less than about 150 nm, for example.Hence, the fifth embodiment is adapted to visually detect methane leaksemanating from a component. FIG. 12 shows the second absorption band 72for methane (see e.g., FIG. 3A). In FIG. 12, the pass band 80 for theoptical bandpass filter 46 of a sixth embodiment is located betweenabout 7600 nm and about 7800 nm with a full width at half maximum lessthan about 200 nm, for example. Thus, the sixth embodiment is alsoadapted to visually detect methane leaks emanating from a component.

FIG. 13 shows an absorption band 98 for ethylene located between about3100 nm and about 3500 nm. In FIG. 13, the pass band 80 for the opticalbandpass filter 46 of a seventh embodiment is located between about 3200nm and about 3500 nm with a full width at half maximum less than about300 nm, for example. Hence, the seventh embodiment is adapted tovisually detect ethylene leaks emanating from a component. FIG. 14 showsanother absorption band 106 for ethylene, which is located between about10000 nm and about 11500 nm. In FIG. 14, the pass band 80 for theoptical bandpass filter 46 of an eighth embodiment is located betweenabout 10450 nm and about 10550 nm with a full width at half maximum lessthan about 100 nm, for example. Thus, the eighth embodiment is alsoadapted to visually detect ethylene leaks emanating from a component.

FIG. 15 shows an absorption band 96 for propylene located between about3100 nm and about 3600 nm. In FIG. 15, the pass band 80 for the opticalbandpass filter 46 of a ninth embodiment is located between about 3200nm and about 3600 nm with a full width at half maximum less than about400 nm, for example. Hence, the ninth embodiment is adapted to visuallydetect propylene leaks emanating from a component. FIG. 16 shows anotherabsorption band 108 for propylene, which is located between about 10000nm and about 11500 nm. In FIG. 16, the pass band 80 for the opticalbandpass filter 46 of a tenth embodiment is located between about 10900nm and about 11000 nm with a full width at half maximum less than about100 nm, for example. Thus, the tenth embodiment is also adapted tovisually detect propylene leaks emanating from a component.

FIG. 17 shows an absorption band 17 for 1,3 butadiene located betweenabout 3100 nm and about 3500 nm. In FIG. 17, the pass band 80 for theoptical bandpass filter 46 of an eleventh embodiment is located betweenabout 3150 nm and about 3300 nm with a full width at half maximum lessthan about 150 nm, for example. Hence, the eleventh embodiment isadapted to visually detect 1,3 butadiene leaks emanating from acomponent. Note that in another embodiment (not shown), the pass band ofthe eleventh embodiment may be located between about 3200 nm and about3400 nm, for example, as another variation. If it is of particularinterest to detect leaks of a certain chemical (or set of chemicals), itis preferred to have the pass band 80 overlaying the absorption bandwhere the area under the absorption band is higher to provide betterdetection sensitivity. The width of the pass band 80 may or may not becritical for a given chemical, depending largely upon the characteristicshape of that chemical's absorption band (e.g., width along wavelengthaxis, height along absorption axis).

FIG. 18 shows another absorption band 112 for 1,3 butadiene, which islocated between about 9000 nm and about 12000 nm. In FIG. 16, the passband 80 for the optical bandpass filter 46 of a twelfth embodiment islocated between about 9000 nm and about 12000 nm with a full width athalf maximum less than about 150 nm, for example. Thus, the twelfthembodiment is also adapted to visually detect 1,3 butadiene leaksemanating from a component. Note that the pass band 80 in FIG. 18 is notcentered on the largest peak 114 of the absorption band 112. In anotherembodiment (not shown), it may be preferred to have the pass band 80centered at or closer to the largest peak 114 of the absorption band112.

FIG. 19 shows an absorption band 116 for sulfur hexafluoride (SF₆)located between about 10000 nm and about 11500 nm. In FIG. 19, the passband 80 for the optical bandpass filter 46 of a thirteenth embodiment islocated between about 10500 nm and about 10600 nm with a full width athalf maximum less than about 100 nm, for example. Thus, the thirteenthembodiment is adapted to visually detect SF₆ leaks emanating from acomponent. Sulfur hexafluoride is often used in switching gear forelectrical equipment and its emissions are harmful to the environment.Hence, an embodiment of the present invention may be used to visuallydetect SF₆ leaks emanating from electrical equipment, for example.

FIG. 20 shows a fourteenth embodiment of the present invention. In thefourteenth embodiment, the refrigeration system 60 of the infraredcamera system 22 has a chamber 126 adapted to retain liquid nitrogentherein. The liquid nitrogen has thermal communication with therefrigerated portion 42 to cool the infrared sensor device 44 andoptical bandpass filter 46 located therein. For the fourteenthembodiment, a currently preferred infrared camera system (22) is theInSb Laboratory Camera by Indigo System, Inc. of California,particularly when made portable (as shown in FIG. 20). The frame 24,battery 36, and display screen 30 may be the same on the fourteenthembodiment (FIG. 20) as that of the first embodiment (FIG. 1). Toprovide for better viewing of the display screen 30 in a brightenvironment, a shroud, hood, or visor may be provided around the displayscreen 30. For example, the fourteenth embodiment shown in FIG. 20 has alight shield 128 located proximate to the screen 30 for partiallyshielding the screen 30 from ambient light. During use, an inspector mayplace his face up to or against the edge of the shroud to shield theenvironmental light from the display screen 30 and allow the inspectorto view the screen with the darkened enclosure formed.

An embodiment of the present invention may be used to inspect any of awide variety of components having the chemical (or chemicals) ofinterest therein, including (but not limited to): a pipe, a compressor,an engine, a valve, a container, a tank, a switch, a reservoir, afitting, a connector, a hose, a flare, an exhaust outlet, a machine, avent for a blow-off valve, and combinations thereof, for example. Someexample uses of embodiments of the present invention will be describednext.

An embodiment of the present invention may be used to visually detectthe evaporation (i.e., fumes) of petroleum products leaking from acomponent, such as a valve or pipe fitting. An advantage of anembodiment of the present invention over prior methods of detectingleaks (e.g., flame pack ionizer, sniffer device) is that the inspectorcan actually see the leak flowing by the visible image (representing theinfrared image) provided by the infrared camera system 22. Using asniffer device, the sensor has to be within the flow stream to detectit, which requires close proximity and thorough scanning to cover anentire component or area. Using an embodiment of the present invention,an inspector can visually scan a large area in a much shorter period oftime, and the inspector can do so from a distance. Thus, the inspectormay not need to climb on and around equipment, which may be dangerous tothe inspector. Also, pipes needing inspection are often located overheadalong a roof, which is difficult to inspect with a sniffer device. Butwith an embodiment of the present invention, an inspector may standbelow the pipes and perform the visual inspection using the infraredcamera system 22 from the ground (from a distance).

Also, an inspector may combine the use of an embodiment of the presentinvention with other inspection methods. For example, after an inspectorlocates a leak visually with the infrared camera system 22 of anembodiment, the inspector could then do a further analysis of the leakusing other measurement tools.

In a first method of using an embodiment of the present invention, anembodiment of the present invention (e.g., first embodiment) is used tovisually inspect a natural gas (methane) regulator station 120. Usually,such regulator stations are enclosed within the boundary of a fence 122.As shown in FIG. 21, an inspector 124 using an embodiment of the presentinvention may inspect the regulator station 120 from a location outsideof the boundary defined by the fence 122, even though the regulatorstation 120 is located within the boundary defined by the fence 122. Ifthe fence 122 cannot be seen through, as with a chain-link fence or asteel tubing fence, the inspector 124 may be able to visually inspectthe regulator station 120 over the fence 122. For example, the inspector124 could stand on an object (e.g., truck bed). As another alternative,an inspector 124 could be lifted by a boom on a boom-truck, for example.Also, the inspector 124 may perform the inspection within the fenceboundary 122.

For most methods of using an embodiment of the present invention tovisually detect a leak of a chemical (or chemicals) emanating from acomponent, the following steps will be performed. An inspector aims theinfrared camera system 22 toward the component or components ofinterest. Infrared images of the component and background enter thecamera system 22 via the lens assembly 40 (at least one lens 38) (seee.g., camera system 22 in FIG. 2). The infrared image passes through theoptical bandpass filter 46 on its way to the infrared sensor device 44.The infrared image is filtered by the optical bandpass filter 46 inaccordance with the characteristics of the filter 46 (i.e., its passband 80). The filtered infrared image is then received by the infraredsensor device 44, which converts the filtered infrared image to anelectrical signal representing the filtered infrared image. Thiselectrical signal is then electronically processed, within the camerasystem 22 (see e.g., FIG. 2) and/or externally by another device outsideof the camera system 22, to provide a visible image representing thefiltered infrared image. This visible image may be viewed in real timeby the inspector, viewed by another person at another location (e.g.,remotely located), recorded, transmitted to another device, transmittedto another location, or combinations thereof, for example.

In a method of the present invention, an inspector may obtain images andevaluate the images while performing the inspection. In another method,the inspector may do the same, and in addition, the images may berecorded and reviewed a second time. The second review may be performedby the same inspector, another person, or by a computer using imagerecognition software. The second review may find anything missed in theoriginal survey. The ability to have a second review is not availablewith many conventional ways of doing leak surveys (e.g., usingflame-packs) because a focused visual image of the inspection is notprovided. Thus, a better leak survey requiring the same time and money(or less) may be performed using a method of the present invention, plusa visual record of the leak may be stored and may be viewed numeroustimes.

An advantage of an embodiment of the present invention is that it mayallow the recording of the images obtained during the visual inspection.Such recordings may be useful in a number of ways. The recorded imageobtained in the field may be transmitted (e.g., in real time or later)to a reviewer (person or computer system) at another location or aremote location. Sometimes in the field where bright conditions existoutside, for example, it may be difficult for the inspector to see smalldetails on the video monitor or display screen. Also, the inspectionconditions may not be conducive to a careful study of the image duringthe inspection. Thus, a reviewer located in a dark and stableenvironment may provide a better review of the images obtained by thesystem. The images may be recorded by a device attached to the infraredcamera system, recorded at a remote location after being transmitted, orrecorded by a separate device not attached to the infrared camera system22, for example. An image may be transmitted from the camera system 22to another device (which may or may not be remotely located) by any of awide variety of communication means, including (but not limited to): acable, a wire, between wireless communication devices, via a networkconnection, via the Internet, or combinations thereof, for example. Theimages provided by the infrared camera system may be recordedcontinuously during an inspection and/or they may be recorded as desiredover any period of time.

Referring to FIG. 21, note that a video recording device is located in acarrying case separate from the infrared camera system. In otherembodiments of the present invention, other components of the system maybe separate from the infrared camera system (e.g., carried in abackpack). This may be preferred so that the camera system may belighter and held easier. An embodiment is contemplated where most of thesystem components are located in a back pack or some other carrying case(e.g., case with wheels and handle) so that the camera portion havingthe lens, optical bandpass filter, and infrared sensors may be locatedin a smaller hand held unit. Such a hand held unit may include a smallflat panel display screen, for example. It is also contemplated that thevisible images from the camera may be displayed to an inspector using asystem that projects the images directly into one or more of theinspector's eyes or onto an interior surface of a eyepiece oreyeglasses. One of ordinary skill in the art will realize many differenttypes and sizes of display screens or projectors that may beincorporated into or used for an embodiment of the present invention.

It is also contemplated that an embodiment of the present invention maybe made intrinsically safe to allow for greater flexibility and usagesof the system for performing inspections. Also, providing an embodimentthat incorporates an intrinsically safe infrared camera system mayprovide the advantage of entering plants for performing inspectionswithout the need for a hot work permit to be issued and/or without theneed for other safety precautions normally associated with the use of anon-intrinsically safe inspection system.

It is further contemplated that an embodiment of the present inventionmay incorporate a halogen light (e.g., attached to the camera system orseparately provided) to provide a greater thermal contrast for thecamera system using the heat radiated by the halogen light to change thetemperature of the background slightly. It may be useful to use thehalogen light on an as needed basis to get a more detailed image (highersensitivity or better image resolution) of a leak after it is located(such as for making a recording of the leak).

The visual identification of a leak may be performed at another locationremote from the infrared camera system and/or remote from the leaklocation, e.g., while viewing a recording of the images, while viewingan image transmitted to the remote location, or combinations thereof,for example. As an example, an inspection team flying over atransmission line in a helicopter (discussed further below) may beconcentrating on obtaining a good image of the transmission line andprecisely following GPS coordinates of the transmission line. While in ahelicopter, it may be difficult for the inspection team to concentrateon reviewing the images obtained during the inspection process. Thevisual images obtained by the infrared camera system may be recorded forand/or transmitted to a reviewer. The reviewer may then carefully reviewthe images to look for leaks. Such review may be performed in real-time,which would allow the reviewer to communicate with and instruct theinspectors to go back to a suspect location for a confirmation (i.e.,hovering over a certain location and obtaining more images of a singlelocation). Or if the visual inspections are recorded, a reviewer maystudy the inspection images at a later time. Hence, one of the membersof the inspection team may later sit down in an environment moreconducive to studying the images to provide the review of the images.Then, if needed or desired, a closer or more lengthy inspection ofsuspect locations may be performed later.

Government safety regulations and rules typically require that gas orpetroleum product transmission lines and distribution lines be inspectedat certain regular intervals. If a company does not comply with suchrules and regulations, the company may be charged steep fines. Also, ifthere is some type of accident or incident where a leaking or rupturedline causes an explosion or fire, the company will want to provideevidence that they were diligent and not negligent in performing aninspection of that line. Hence, another benefit of being able to recorda focused image of the visual inspection is the ability to have a recordof the inspection. In an embodiment of the present invention, GPScoordinates, a date stamp, and/or a time stamp may be recorded onto orembedded within the recorded images of the visual inspection. This willprovide evidence that an inspection was performed for a particularlocation at a particular date and time. Such records may be stored (inanalog or digital format) on some type of storage medium (e.g., videotape, CD, DVD, database, hard drive, etc.) for future reference.

In a preferred embodiment and/or method of the present invention,inspection information may be displayed and or recorded along with therecording/displaying of the visible image representing the filteredinfrared image. The inspection information may include any relevantinformation desired, including (but not limited to): inspection locationname, inspection location address, component name, componentidentification information, global positioning coordinates, a date, atime of day, an inspector's name, an inspection company's name, one ormore camera system setting values, or combinations thereof, for example.Also, voice notes may be recorded onto or along with the images on amedium (e.g., voice notes recorded on a video of inspection). Suchinspection information may be embedded within the visible image or maybe recorded and tracked separately (e.g., in a separate file, as aheader file, etc.).

In a second method of the present invention, an embodiment of thepresent invention may be used to inspect numerous fenced yards 130 froma single location, from outside the yards 130, and/or from a single yard130. FIG. 22 shows a housing configuration found in many neighborhoods,where there is no alley behind the houses 132. Instead, only a fence 134may separate two or more adjacent backyards 130. In FIG. 22, anunderground natural gas distribution line 136 is shown in dashed lines,which run across numerous backyards 130. Using conventional leak surveytechniques, an inspector would need to enter each backyard 130 toinspect the line in all six of the yards 130 shown in FIG. 22. However,because a leak may be detected visually using an embodiment of thepresent invention, an inspector may enter only one backyard 130 and seeinto each of the adjacent yards 130 (as indicated by the arrows in FIG.22). Thus, only one customer needs to be disturbed for the inspection,rather than six. Also, an inspector may attach the infrared camerasystem 22 to a boom on a truck, or he may be standing in the boomholding the camera system 22, located at an end of a street or in analley to obtain visual access to numerous backyards 130. Thus, using anembodiment of the present invention, multiple backyards may be surveyedfor line leaks visually using an infrared camera system 22 from a singlelocation (e.g., from a single backyard 130 looking over the fences 134,or from a boom).

Many residential meters for natural gas are located next to a house(e.g., between houses), remote from where a vehicle may drive. Suchdistribution lines must be periodically tested for leaks. In such cases,using a conventional method of leak surveying, the inspector typicallywalks to each meter to perform the leak survey. In a third method of thepresent invention, such meters and distribution lines may be surveyedvisually using an infrared camera system from a vehicle. For example, aninspector may aim an infrared camera system at the distribution lineswhile driving past each home without leaving the street or the vehicle.This can save a great deal of time and money for saved man hours. Thissame technique of using an embodiment of the present invention may beused for inspecting components located adjacent to or on any building,not just residential houses.

In a fourth method of performing an inspection with an embodiment of thepresent invention, the inspection may be performed in stages. A firststage may be that the inspector views the area of inspection using theinfrared camera system from a distance to make sure there is not a hugeleak that the inspector is about to walk or drive into. This would bemainly for the safety of the inspector. Many chemicals have little or noodor and are invisible to the human eye. Hence, an inspector could bedriving or walking right into a very dangerous situation. Next, afterthe inspector confirms that there is not a huge leak (e.g., large flowof chemical emanating from the site), the inspector can perform a moredetailed inspection looking for medium, small, and/or very small leaks.

Sometimes gas or chemical leaks or chemical spills in cities or nearhighways are reported to the police first, and the police send outofficers to direct traffic away from the gas/chemical leak for thesafety of the public. However, there have been instances where anofficer drives right into the stream of the leak without knowing it andignites an explosion, which may injure or kill the officer. The samedangers exist for repair persons entering such a location. Thus, itwould be beneficial to incorporate a method of using an embodiment ofthe present invention into a first response system. For example, if achemical leak/spill is suspected, a helicopter with an infrared camerasystem of an embodiment may be flown toward the suspected location toassess it visually from a safe distance using a method of the presentinvention. By doing so, the magnitude and direction of the fumes from aleak or spill may be determined and reported quickly and safely. It isoften difficult to initially determine the magnitude of the leak orspill using conventional methods. As another example, an embodiment ofthe present invention could be used by firemen from their fire truck asthey approach a scene of a reported leak or spill. Likewise, amaintenance or safety crew at a processing plant equipped with anembodiment of the present invention could assess a situation from a safedistance as they enter to investigate a suspected leak or spill.

The aiming of the infrared camera system of an embodiment towards acomponent being inspected may be performed from a vehicle. Part or allof the system may be attached to the vehicle or supported by thevehicle, and/or may be held be a person in the vehicle, for example. Itmay be any type or kind of vehicle suitable for the inspection,including (but not limited to): a truck, a car, a motorcycle, a bicycle,a boat, a ship, a personal watercraft, a fixed-wing airplane, a rotarywing vehicle (e.g., helicopter, gyro-plane), a powered paraglider, anultralight aircraft, a powered glider, a glider, a balloon, a blimp, aremote controlled vehicle, an unmanned aerial vehicle, and combinationsthereof. The vehicle may be moving or stopped during part or all of theinspection. If the infrared camera system is mounted on or attached to avehicle, it may be desirable to have the camera system mounted on sometype of stabilizing platform or stand, as is commonly used in the moviefilming industry (e.g., gyro-stabilized apparatus). Such a stabilizingplatform may provide the ability to obtain better images of a test sitefrom a moving vehicle (e.g., truck, ATV, helicopter, blimp, airplane).

An embodiment may be attached to a satellite to provide inspections fromspace. One of the advantages of infrared is that it can see through mostclouds. The range of inspection is limited only by a line of sight for amethod of inspecting using an embodiment of the present invention.Hence, as long as the chemical leak or the trail of fumes emitted fromthe leak are within a line of sight (e.g., not blocked by trees, heavyrain, buildings, or structures), an infrared image may be obtained. Thesize/type/configuration of lens can thus be increased/decreased/variedas needed to provide focus for a given range.

The typical method of finding leaks on cross country transmission linesis to walk along the lines using a sniffer device (flame-pack detector),or in some cases where there are no fences one may drive a truck or ATVwith mounted sniffers, up and down the lines. One of the disadvantagesof this method is that if the wind is blowing away from the sniffer orif the vehicle or the walker is upwind from the leak, the snifferprobably will not detect a leak; thus missing the leak altogether. Thenext problem is that a lot of the gathering lines have now beenovergrown with houses, buildings, and backyard fences. This makes itvery impractical to check for leaks in and around residential back yardsusing conventional techniques. Companies often perform aerial surveys tolook for encroachments or blocking of their easement. Such surveys maybe performed simultaneous with a visual infrared inspection for leaks.

Also, truck mounted sniffers are actually built for leak detection inthe cities not for cross country transmission lines. The differencebeing that the size of leak in cities versus transmission lines can begreat. There is a danger of a pickup with a hot catalytic converter withgrass stuck to it being driven onto a 200 mcf per day leak. Such ascenario can result in an explosion that can kill the driver and destroythe equipment. The conventional leak survey equipment requires theinspector to be in close proximity within the stream of gas flow todetect it. By the time the gas is detected for a large leak, it may betoo late. Using an embodiment of the present invention, a large leak maybe seen from more than ½ mile away, and other leaks may be seen from adistance.

An embodiment of the present invention may be attached to a helicopteror plane, for example, and flown over a transmission line at arelatively high rate of speed (e.g., 60-120 mph) while visual images arerecorded using the infrared camera system. Even though the speed may betoo great for an inspector to spot a leak on-the-fly, a computer imagerecognition system may be able to detect the leak at the higher speed,or a second review playing back the recording at a slower speed may beable to catch missed leaks.

Often the leaks in transmission lines are found by locating deadvegetation where the gas is leaking through the ground. However, duringthe winter when the grass is brown, this method may not work. Also insome areas, such as desert areas, there may be no vegetation where theleak exists. Thus, using a method of the present invention, leaks from aburied transmission line may be easily detected visually from a short orlong distance away with an embodiment of the present invention.

Down in the swamp land of southern Louisiana, for example, it is almostimpossible to walk the lines. Instead, the operators typically fly overtheir lines and look for discolored vegetation. However, a colony ofants can also leave an area of discolored vegetation that looks like agas leak from the air. With an embodiment of the present inventionmounted on a helicopter, for example, one may hover over an areasuspected of having a leak, and record a short sequence of the specificarea using the infrared camera system 22 to easily determine if there isa leak. In alternative, the entire line may be visually scanned using aninfrared camera system 22 to look for leaks.

Most transmission lines have pressure gauges and automated valves atcertain intervals (check points) along the line. Often an operator hasthe equipment to see a pressure drop across the line between pointswhich may be 50-100 miles apart, for example. Along such a long distancebetween the two points, there may be several leaks. Typically, it isdifficult to determine which of the leaks is larger. Thus, many smallerleaks may be fixed before finding the larger leak. Using an embodimentof the present invention, the larger leaks may be distinguished from thesmaller leaks. Thus, the larger leaks may be located and repaired first,as they are usually the first priority.

Sometimes when one leak is being repaired, it can cause a new leak inthe same pipe at another location due to movement of the pipe during therepair operation. In a method of the present invention, the nearbyportions of the repaired line may be quickly and easily inspectedvisually using an embodiment of the present invention to determinewhether another leak exists along that line.

When cast iron or old metal lines develop leaks, the pipe material oftenbecomes saturated with the leaking gas. Also, the dirt around and abovea gas leak (for any type of pipe) often becomes saturated with gas.Thus, after performing a repair and replacing the dirt, a snifferdetector may falsely indicate that the leak is still present because itmay be detecting the remaining gas saturated in the dirt and/or pipe.Also, if the gas is odorized, the smell will often linger for severaldays as it slowly dissipates from the dirt, which can lead to follow-upcomplaints by persons still smelling the gas. However, performing avisual gas leak inspection with an embodiment of the present invention,may quickly determine whether the leak still exists after the repairs(before or after replacing the dirt). In most cases, the visual testwill be able to distinguish remaining petroleum products saturated inthe dirt and an actual leak (showing a stream of blowing gas, forexample). This can save companies a lot of money on service calls andensure that the leaks are actually fixed more accurately and morereliably.

Leak surveys in downtown business districts often have to be conductedat night due to traffic. With proper flight clearance, an infraredcamera system 22 may be mounted on a helicopter, for example, to performthese leak surveys from a helicopter during the daytime and saveovertime hours for crews. One of the advantages of performing a leaksurvey from above using an infrared camera system 22 to visually detectleaks is that the ground often retains heat to provide a good thermalcontrast and thus a better background contrast for viewing the leak withinfrared, as compared to the sky or a structure in many cases.

Another method of using an embodiment of the present invention is thedetection of leaks in large tanker vessels transporting petroleumproducts by sea. Using an infrared camera system of an embodiment of thepresent invention, leaks to the environment may be detected visuallyfrom a safe distance (e.g., on land, on a dock) by the shipping companyor by enforcement/regulatory agencies (e.g., EPA, DOT). Such shipscarrying chemicals or petroleum products may be visually inspected asthey pass by or as they approach, for example.

Inspections may also be performed onboard the boat, ship, or vessel.Also, enclosed areas within a ship may be periodically or continuouslymonitored using a portable or permanently-installed/stationary infraredcamera system of an embodiment, for example.

Another method of using an embodiment of the present invention isdetecting gas leaks on petroleum production rigs. Often such rigs areapproached via helicopter. An infrared camera system 22 adapted tovisually image a petroleum product leak may be mounted on a crewhelicopter. This would enable the crew on the helicopter to scan for gasleaks on gas platforms out in the ocean as they approach and before theyland, for example. This would reduce or eliminate the risk of landing ahelicopter with a hot engine into a gas leak. Furthermore, in anotherembodiment, a permanently-mounted/stationary infrared camera system 22may be mounted at certain locations around the rig to provide acontinuous or periodic visual leak survey.

In another method of using an embodiment of the present invention,detection of chemical leaks may be performed at factories, processingplants, manufacturing facilities, refineries, and/or petroleumseparation plants. At some plants, they typically do monthly valvemaintenance and inspections, for example. The problem with the way thatthey are currently done is that the flame-pack detector will oftentrigger on grease or WD-40 that is used on the valves for lubrication,for example. However, an infrared camera system 22 may be tuned (e.g.,using an optical bandpass filter 46 having a certain pass band 80) sothat it does not have the ability to see or detect these greases andlubricants. Hence, such an embodiment may distinguish between thelubricants and gas leaks. If the fumes of the greases and/or lubricantsare imaged by the camera system 22, the visual observation of the fumesand the pattern of the fumes may allow the inspector to discern that itis not a leak and it is merely a lubricant evaporating. Often valveshave been repacked due to a false leak detection triggered by lubricantson the valves, which is very costly and a waste of resources.

Another method of the present invention is the detection of leaks in thepetrochemical industry or other chemical producing industries, using anembodiment of the present invention to visually detect leaks. Detectionof such leaks may be performed at any stage from the exploration to theprocessing and production to the transporting of the chemicals producedto the containers storing the chemicals to the equipment using thechemicals, for example. A pipe or transportation line carrying thechemical may be visually inspected for leaks using an embodiment of thepresent invention. As another example, various pipes, connections, andequipment at a processing plant may be visually inspected or monitoredfor leaks using an embodiment of the present invention. Storagecontainers, cargo vessels, or truck trailers used for storing and/ortransporting the chemicals may be visually inspected for leaks using anembodiment of the present invention, for example. Some example chemicalsinclude (but are not limited to): ethylene, propylene, acetylene,propane, alcohol, ethanol, methanol, xylene, benzene, butadiene,acetone, compounds thereof, and combinations thereof.

An embodiment of the present invention may be used to perform a leaksurvey in and/or around a plant. An advantage of the present inventionis that large leaks can be distinguished from small leaks, visually.Often the small leaks go unrepaired because they cannot be found easilyusing conventional methods. Even small leaks can be very dangerous in anenclosed area where flammable gases become trapped therein. Also, inmany processing plants, the gases may have no odor added to them, whichmeans a person would not smell the gases. Even where the gases areodorized, it is often difficult or impractical to detect all of theleaks. In most processing plants, the plant smells like chemicalseverywhere because there are lots of small leaks. If the plant personnelcould quickly and easily find the leaks, as they can using an embodimentof the present invention, it may become economical to fix even thesmallest leaks. If that becomes the case, then processing plants maycease to smell like chemicals all the time. On one test of an embodimentof the present invention, 15 leaks were found in one region of a largeplant in just 30 minutes, which is faster than most conventional methodsof inspection. Another advantage of using an embodiment of the presentinvention is that the inspector often does not have to crawl on andaround the equipment and pipes to find the leaks, as they may be seenwith the infrared camera system when a line of sight is provided. Usinga sniffer detector, however, an inspector would be required to get hisdetector within the flow of the gas leak to detect it.

Enclosed areas within a plant or any area at a plant may be periodicallyor continuously monitored using a portable orpermanently-installed/stationary infrared camera system of anembodiment, for example. A permanently-mounted infrared camera of anembodiment may use a closed-cycle Stirling cryocooler, for example, andmay be similar to the first embodiment of FIG. 1 but adapted to bemounted in a building. An entire network of permanently mounted camerasmay be strategically located throughout a plant to provide partial orcomplete coverage of the plant. In one embodiment, a person may monitorthe images provided by the cameras continuously or periodically. Inanother embodiment, a computer system with image recognition softwaremay be used to detect changes in the image or motion in an imageindicating a stream of gas or liquid flow at a leak.

Also, many plants or factories have blow-off valves that vent out of theroof. A single plant may have numerous vents with vent exits being morethan 30 feet high. However, using an infrared camera system inaccordance with the present invention, gases exiting such vents may bequickly surveyed from a distance on the ground, for example. Also, flareemissions burning on the top of a tower structure may be visuallyinspected using an embodiment of the present invention from a distance(e.g., more than 10 feet away, from the ground, etc.).

Recorded inspection data from prior inspections may be useful for aplant manager. If an inspection is performed in a plant and the sameleak is found again in a subsequent survey, as documented visually withvideo by inspectors, the plant manager can then know that either theleak was never repaired or it is a re-occurring leak.

In yet another method of using an embodiment of the present invention,government regulatory agencies (e.g., railroad commission, DOT, EPA) maythemselves perform visual inspections easily and quickly using aninfrared camera system to determine if a plant or factory is emittingpetroleum products or other chemicals that should not be emitted intothe environment (e.g., volatile organic compounds, volatile inorganiccompounds, nitrous oxide, unburned chemicals, etc.). Such inspections bygovernment regulatory agencies may be performed randomly as surpriseinspections to enforce stricter compliance with environmental rules andregulations. Also, government regulatory agencies may require recordingsof inspections to be retained so that they can review them. Furthermore,a government regulatory agency may then perform follow-up inspectionsvisually at targeted areas where a leak was known from a priorinspection to ensure that the leaks were repaired in a timely manner. Agovernment regulatory agency may also review a series of test videos tolook for unrepaired leak scenarios. Thus, there are numerous methods ofusing an embodiment of the present invention that may be useful to agovernment regulatory agency.

In another method of the present invention, fuel leaks (or otherchemical or fluid leaks) on a vehicle may be easily found using anembodiment of the present invention. For example, on a Lotus Esprit car,the gas tanks are notorious for rusting and developing small pinholeleaks which are difficult to locate and find. It is not cost efficientto remove the gas tanks for inspection, as the engine must be removed toget the gas tanks out of the vehicle. Also, such cars are notorious forhaving leaks at high pressure and/or low pressure fuel lines, which cancause engine fires. Furthermore, the toxic fumes from an engine baywhere a fuel leak exists often make there way into the cabin, which isdangerous and obnoxious for the cabin occupants. An embodiment of thepresent invention may be used to accurately pinpoint and find suchleaks. Also, such a method may be applied to locate fuel leaks in othervehicles, such as airplanes, boats, helicopter, and personal watercraft,for example. An infrared camera system 22 of the present invention maybe used to locate refrigerant leaks quickly on a vehicle. Also, anembodiment of the present invention may be used to locate gas orrefrigerant leaks in home or building HVAC equipment.

FIGS. 23A-31B are some images generated by an embodiment of the presentinvention during experimental testing. Specifically, FIGS. 23A-31B weregenerated using the fourteenth embodiment (see FIG. 20) having anoptical bandpass filter 46 with a pass band 80 about the same as thatshown in FIG. 4.

FIGS. 23A-23D are visible images representing filtered infrared imagesof a gas 140 leaking from the ground (e.g., a buried line). The imagesof FIGS. 23A-23D are from a sequence of images extracted from a videorecording of this leak 140. Although sometimes difficult to illustratein still images, the movement of the leak stream 140 in a video(sequence of images) makes the leak 140 much more apparent. Very smallleaks (low flowrate) that do not show up in one still image are ofteneasily seen in a video because the movement of the leak stream or fumescan be seen in a video.

FIGS. 24A-24D are images obtained by an embodiment of the presentinvention showing a gas 140 leaking from a compressor at a flange 142 onthe discharge side. The sequence of images in FIGS. 24A-24D wereextracted from a video showing the gas 140 streaming from the flange142.

FIGS. 25A-25D are images obtained by an embodiment of the presentinvention showing a natural gas (methane) leak 140 resulting from a crewcutting 1½ inch gas line with approximately 12 psi pressure. It is anunderground gas line (not shown). Although the large cloud of methane140 exiting the hole in the ground is somewhat dispersed and difficultto see in the still images of FIGS. 25A-25D, it is easily seen in thevideo due to the movement of the cloud 140. Note also that the images ofbackground objects are easy to discern and focused in the originalvideo, which aids in providing a context of where the leak 140 is comingfrom.

FIG. 26 is an image obtained by an embodiment of the present inventionand extracted from a recorded video sequence. FIG. 26 shows a large gasleak 140 emanating from a component 144 in a processing plant.

FIG. 27 is also an image obtained by an embodiment of the presentinvention and extracted from a recorded video sequence. FIG. 27 shows agas 140 flowing from a vent tube 146 extending from a building roof 148(about 30 feet high). This image was obtained by a person at groundlevel. The gas flowing out of the vent 146 may be from a blow-off valvethat is exhausting to the environment, which may be indicative of acondition at that component causing the blow-valve to be opened.

FIGS. 28A and 28B are more images obtained by an embodiment of thepresent invention and extracted from a recorded video sequence. FIGS.28A and 28B show a man pumping gasoline into his truck at a gas pump.Note in FIG. 28B that as the gas is pumping into the gas tank, the gasfumes 140 can be seen just above the pump handle with the truck bed asthe background.

FIG. 29 shows an image of propane 140 exiting a propane bottle in a testof the system for detecting propane. FIG. 30 shows an image of a smallgas leak 140 emanating from a component at a processing plant. The leakappears as a faint black cloud 140 in the image. This is a relativesmall leak.

FIGS. 31A and 31B are images taken from a helicopter flying over a testsite. In this test, a propane bottle was opened, as in FIG. 29, in afield. In FIG. 31A, the propane stream 140 can be seen with the infraredcamera system at ½ mile away while the helicopter is moving toward thetest site at about 60 knots. FIG. 31B is a more focused image of thepropane stream 140 at a closer distance than that of FIG. 31A. Note thata person 150 can be seen standing next to the propane stream 140 andnext to a bush 152 in FIG. 31B. Also, note that two roads can be seen inFIGS. 31A and 31B, which provide reference points and context of thelocation of the propane stream 140.

An advantage of an embodiment of the present invention, as illustratedin these images of FIGS. 23A-31B, is that often the background andsurrounding objects can be clearly seen in the image along with the leakor stream of gas 140. This can be very useful in providing a referenceor context of where the leak is located and aids in documenting the leakusing video images.

In a recent test of an embodiment of the present invention before the USEPA, in comparison with other infrared camera systems, the embodiment ofthe present invention greatly outperformed the other systems. After thistest before the US EPA, new US EPA regulations are expected to bereleased by the end of 2004, or shortly thereafter, allowing for the useof infrared camera systems to perform visual leak surveys. Thisdemonstrates a long felt need in the industry that others have failed tomeet, and that an embodiment of the present invention is now able tofulfill.

Also, after the US EPA test described above, there has been an explosivedemand for embodiments of the present invention and for services usingan embodiment of the present invention. This demonstrates the commercialsuccess and great demand for embodiments of the present invention andfor services using embodiments of the present invention.

FIG. 32 illustrates a schematic of a first dual camera embodiment of thepresent invention. This system includes a first video camera 22, whichis an infrared camera system with an optical bandpass filter 46(preferably installed in a refrigerated portion 42 thereof, i.e., coldfilter configuration); a second video camera 154 (e.g., another infraredcamera system); an image splitter 156; a lens assembly 158; and an imageprocessor/recorder 160. The second video camera 154 may be any infraredcamera system that can obtain an image from the same type of lens as thefirst video camera 22. The second video camera 154 may be an infraredcamera with filters so that it will not image the leaking chemical. Thefirst video camera 22 is an infrared camera adapted to provide a focusedvisual image of a chemical leak by using an optical bandpass filter 46for a specific pass band 80 (e.g., pass band 80 with a wavelength rangecentered at about 3.38 microns). For example, the first video camera 22may be any of the embodiments discussed above (see e.g., FIGS. 1-20).The first video camera 22 may receive the same image as the second videocamera 154 from the same lens 158 via the image splitter 156. The videosignal from each camera may be output to the image processor/recorder160. The image processor/recorder 160 may simply record the two videofeeds for later processing. In an alternative, the imageprocessor/recorder 160 may be a system (e.g., a computer system runningsoftware for processing the video data) or specialized/dedicatedhardware for processing the two video feeds. Preferably, the images fromthe second video camera 154 are compared to the images from the firstvideo camera 22 by a software program running on a computer system.Because a gas leak, for example, will not appear in the image from thesecond video camera 154, the presence of the gas plume shown in theinfrared image from the first camera 22 may be detected as a differencein the two video feeds.

In one embodiment, the software may automatically identify and map thepixel locations in the images for these differences corresponding to thegas plume in the infrared image. Then, the image of the gas plume (thedifferences shown in the infrared images from the first camera) ishighlighted or colored to make it stand out in the image.

Optionally, the image processor/recorder 160 may be communicably coupledto a video monitor 162 (see FIG. 32) and/or a database 164, for example.The video monitor 162 may be used for an operator or inspector to viewany one or more of the images or all of the images obtained while usingthe system 20, for example. The database may be used as a repository orarchive for the collected video images and test results. The first andsecond cameras 22, 154 may be separate devices. In another embodiment,the image splitter 156, lens 158, first camera 22, and second camera 154may be integrally placed within a single portable unit. Likewise, theimage processor/recorder 160 (or some portion thereof) may be placedwithin the same enclosure or on the same rack as the remainder of thesystem 20.

FIG. 33 is a flowchart 168 showing an illustrative method that may beused for an embodiment (e.g., the embodiment shown in FIG. 32) of thepresent invention. In this method of FIG. 33, the images from bothcameras may be recorded in the field and later processed in a vehicle oroffice. Also, using the method of FIG. 33, the images of both camerasmay be stored before being processed, even though the processing may beperformed immediately thereafter (on-the-fly). The images from bothcameras are compared to identify the differences (see block 170), whichmay be indicative of chemical leak. Next, the differences are identifiedand mapped out. The mapped differences may then be added to the imagefrom the second camera to provide a composite image. Also, whendifferences are identified (e.g., exceeding a predetermined number ofpixels within the image, detecting movement), an alarm may be triggeredto notify an operator or inspector of the suspected detection of achemical leak.

In another method, illustrated in FIG. 34, the infrared image from thefirst camera 22 and the composite image may be recorded. For example,the infrared image from the first camera may be needed for recordkeeping to maintain an unmodified image. However, the composite imagemay be preferred for reviewing by the inspections or for studying theinspections, as it may provide color coding or other visual or audiocues to help the reviewer to better identify potential leaks.

In still another method, illustrated in FIG. 35, only the compositeimage may be recorded and the processing of the images may be performedas the images are collected. However, a temporary buffer memory (e.g.,DRAM, MRAM) may be used during the processing.

FIG. 36 shows a simplified schematic for an alternative system 20 wherethe image splitter and mutual lens are not used. Thus, the first camera22 receives its images separately from the second camera 154. In thisconfiguration, the second camera 154 may be a visible light camera, forexample. FIG. 37 shows an illustrative flowchart 172 for a method wherethe system 20 of FIG. 36 may be used. The method of the FIG. 37flowchart may be varied to provide a recording of the image(s) from thefirst and/or second cameras 22, 154. In other embodiments (not shown),additional camera(s) may be used as well (e.g., third camera). A videoimage from the second video camera 154 may be shown within a video imagefrom the first camera 22 (picture-in-picture) to provide a referenceview (e.g., full color visible light image) for the infrared image fromthe first camera 22.

FIG. 38 shows an illustrative flowchart 174 for a method of anembodiment of the present invention. In this method, an alarm may betriggered if the comparison of images from the first and second camerasshows sufficient differences above a predetermined threshold (e.g., areaof pixels, number of pixels, number of pixels per area, etc.) ormovement in the image from the first camera that is not in the imagefrom the second camera.

In another embodiment, one stationary-mounted camera (e.g., in an engineroom) may be used. Often in certain areas of a plant there is rarelymovement (e.g., no people moving about the room most times) in the room(other than unseen internal parts). In such embodiment, the image may bemonitored by hardware or a computer system to detect movement in theimage. Because the image is an infrared image taken with an infraredcamera system of an embodiment, the movement may be caused by a chemicalleak. Thus, the image may be continuously or periodically monitored formovement automatically. An alarm may be triggered when movement isdetected to alert an operator to the suspected leak. Then, the operatormay view the video image (past or present) to see if there is an actualleak.

In accordance with another aspect of the present invention, a passiveinfrared camera system adapted to provide a visual image of a chemicalemanating from a component having the chemical therein, is provided. Thepassive infrared camera system includes a lens, a refrigerated portion,and a refrigeration system. The refrigerated portion includes therein aninfrared sensor device adapted to capture an infrared image from thelens, and an optical bandpass filter located along an optical pathbetween the lens and the infrared sensor device, wherein at least partof a pass band for the optical bandpass filter is within an absorptionband for the chemical. The refrigeration system is adapted to cool therefrigerated portion of the infrared camera system.

The refrigeration system may include a chamber adapted to retain liquidnitrogen, for example. As another example, the refrigeration system mayinclude a closed-cycle Stirling cryocooler. The refrigeration system mayinclude a cryocooler system adapted to cool the infrared sensor deviceand the optical bandpass filter to a temperature below about 100 K. Thepassive infrared camera system is preferably portable and furtherincludes a battery adapted to provide power for the infrared camerasystem during use of the infrared camera system. The passive infraredcamera system may include a frame, a shoulder-rest portion extendingfrom the frame, and a handle extending from the frame. The passiveinfrared camera system preferably includes a flat-panel screen adaptedto display images obtained by the infrared camera system during use ofthe infrared camera system. The passive infrared camera system mayfurther include a light shield located proximate to the screen andadapted to at least partially shield the screen from ambient light.

The optical bandpass filter may be adapted to allow a transmittancegreater than about 45% of infrared light between about 3360 nm and about3400 nm to pass therethrough, for example. As another example, theoptical bandpass filter may be adapted to allow a transmittance greaterthan about 45% of infrared light between about 3350 nm and about 3390 nmto pass therethrough. The pass band of the optical bandpass filter mayhave a center wavelength located between about 3360 nm and about 3400nm, for example. As another example, the pass band of the opticalbandpass filter may have a center wavelength located between about 3375nm and about 3385 nm, wherein the bandpass filter is adapted to allow atransmittance greater than about 80% of infrared light between about3365 nm and about 3395 nm to pass therethrough, wherein the bandpassfilter comprises a silicon dioxide substrate, and wherein the pass bandhas a full width at half maximum transmittance that is less than about80 nm. As yet another example, the pass band of the optical bandpassfilter may have a center wavelength located between about 3340 nm andabout 3440 nm, wherein the bandpass filter is adapted to allow atransmittance greater than about 70% at the center wavelength, andwherein the pass band has a full width at half maximum transmittancethat is less than about 100 nm. As still another example, the pass bandof the optical bandpass filter may have a center wavelength betweenabout 3360 nm and about 3380 nm, wherein the bandpass filter is adaptedto allow a transmittance greater than about 70% at the centerwavelength, and wherein the pass band has a full width at half maximumtransmittance that is less than about 100 nm.

The infrared sensor device may include an Indium Antimonide focal planearray, wherein the focal plane array is enclosed in an evacuated Dewarassembly. The pass band may have a full width at half maximumtransmittance that is less than about 600 nm, for example. As anotherexample, the pass band may have a full width at half maximumtransmittance that is less than about 400 nm. As yet another example,the pass band may have a full width at half maximum transmittance thatis less than about 200 nm. As still another example, the pass band mayhave a full width at half maximum transmittance that is less than about100 nm. The pass band for the optical bandpass filter may be locatedbetween about 3100 nm and about 3600 nm, for example. As anotherexample, the pass band for the optical bandpass filter may be locatedbetween about 3200 nm and about 3500 nm. As yet another example, thepass band for the optical bandpass filter may be located between about3300 nm and about 3500 nm. The pass band for the optical bandpass filtermay have a center wavelength located within the absorbance band for thechemical.

The component being inspected may be a pipe, a compressor, an engine, avalve, a container, a tank, a switch, a reservoir, a fitting, aconnector, a hose, a flare, an exhaust outlet, a machine, a vent for ablow-off valve, or combinations thereof, for example. The refrigeratedportion may be defined by an interior of a Dewar container. The chemicalmay be methane, ethane, propane, butane, hexane, ethylene, propylene,acetylene, alcohol, ethanol, methanol, xylene, benzene, butadiene,formaldehyde, acetone, gasoline, diesel fuel, or combinations thereof,for example. The chemical may be petroleum, petroleum by-product,volatile organic compound, volatile inorganic compound, or combinationsthereof, for example. The chemical may include a hydrocarbon, forexample. As another example, the chemical may include methane, whereinthe absorption band is at least partially located between about 3100 nmand about 3600 nm, wherein the pass band is located between about 3100nm and about 3600 nm. The chemical may include methane, wherein theabsorption band is at least partially located between about 7200 nm andabout 8200 nm, wherein the pass band is located between about 7200 nmand about 8200 nm, for example. As yet another example, the chemical mayinclude sulfur hexafluorine, wherein the absorption band is at leastpartially located between about 10400 nm and about 10700 nm, wherein thepass band is located between about 10400 nm and about 10700 nm. As stillanother example, the chemical may include ethylene, wherein theabsorption band is at least partially located between about 3100 nm andabout 3500 nm, wherein the pass band is located between about 3100 nmand about 3500 nm. The chemical may include ethylene, for example,wherein the absorption band is at least partially located between about10400 nm and about 10700 nm, wherein the pass band is located betweenabout 10400 nm and about 10700 nm. As another example, the chemical mayinclude propylene, wherein the absorption band is at least partiallylocated between about 3100 nm and about 3600 nm, wherein the pass bandis located between about 3100 nm and about 3600 nm. As yet anotherexample, the chemical may include propylene, wherein the absorption bandis at least partially located between about 10000 nm and about 11500 nm,wherein the pass band is located between about 10000 nm and about 11500nm. As still another example, the chemical may include 1,3 butadiene,wherein the absorption band is at least partially located between about3100 nm and about 3200 nm, wherein the pass band is located betweenabout 2900 nm and about 3200 nm. As a further example, the chemical mayinclude 1,3 butadiene, wherein the absorption band is at least partiallylocated between about 9000 nm and about 12000 nm, wherein the pass bandis located between about 9000 nm and about 12000 nm.

The passive infrared camera system may include a video recording deviceadapted to record images obtained by the infrared camera system duringuse of the infrared camera system. The infrared camera system may benon-radiometric. The infrared camera system is preferably portable andnon-radiometric.

In accordance with yet another aspect of the present invention, apassive infrared camera system adapted to provide a visual image of achemical emanating from a component having the chemical therein, isprovided. The passive infrared camera system includes a lens, arefrigerated portion, and a refrigeration system. In this case, therefrigerated portion includes therein an infrared sensor device adaptedto capture an infrared image from the lens, and an optical bandpassfilter located along an optical path between the lens and the infraredsensor device, the optical bandpass filter having a pass band with afull width at half maximum transmittance being less than about 600 nm,wherein at least part of the pass band for the optical bandpass filteris within an absorption band for the chemical. The refrigeration systemis adapted to cool the refrigerated portion of the infrared camerasystem.

In accordance with still another aspect of the present invention, apassive infrared camera system adapted to provide a visual image of achemical emanating from a component having the chemical therein, isprovided. The passive infrared camera system includes a lens, arefrigerated portion, and a refrigeration system. In this case, therefrigerated portion includes therein an infrared sensor device adaptedto capture an infrared image from the lens, and an optical bandpassfilter located along an optical path between the lens and the infraredsensor device, wherein a pass band for the optical bandpass filter islocated between about 3100 nm and about 3600 nm. The refrigerationsystem is adapted to cool the refrigerated portion of the infraredcamera system.

In accordance with a further aspect of the present invention, a passiveinfrared camera system adapted to provide a visual image of a chemicalemanating from a component having the chemical therein, is provided. Thepassive infrared camera system includes a lens, a refrigerated portion,a refrigeration system, and a battery. The refrigerated portion includestherein an infrared sensor device adapted to capture an infrared imagefrom the lens, and an optical bandpass filter located along an opticalpath between the lens and the infrared sensor device, wherein at leastpart of a pass band for the optical bandpass filter is within anabsorption band for the chemical. The refrigeration system is adapted tocool the refrigerated portion of the infrared camera system. The batteryis electrically coupled to the infrared camera system, the infraredcamera being adapted to be powered by the battery during use of thechemical leak inspection system.

In accordance with another aspect of the present invention, a portablechemical leak inspection system that includes a passive infrared camerasystem adapted to provide a focused visual image of a chemical emanatingfrom a component having the chemical therein, is provided. The passiveinfrared camera system includes a lens, a refrigerated portion, and arefrigeration system. The refrigerated portion includes therein aninfrared sensor device adapted to capture an infrared image from thelens, and an optical bandpass filter located along an optical pathbetween the lens and the infrared sensor device, wherein at least partof a pass band for the optical bandpass filter is within an absorptionband for the chemical. The refrigeration system is adapted to cool therefrigerated portion of the infrared camera system. The portablechemical leak inspection system also includes a battery, a frame, ashoulder-rest portion, and a handle. The battery is electrically coupledto the infrared camera system, the infrared camera being adapted to bepowered by the battery during use of the chemical leak inspectionsystem. The frame is attached to the infrared camera system. Theshoulder-rest portion extends from the frame. And, the handle extendsfrom the frame.

In accordance with yet another aspect of the present invention, aportable chemical leak inspection system that includes a passiveinfrared camera system adapted to provide a focused visual image of achemical emanating from a component having the chemical therein, isprovided. The passive infrared camera system includes a lens, arefrigerated portion, and a refrigeration system. In this case, therefrigerated portion includes therein an infrared sensor device adaptedto capture an infrared image from the lens, and an optical bandpassfilter located along an optical path between the lens and the infraredsensor device, wherein a pass band for the optical bandpass filter islocated between about 3100 nm and about 3600 nm, and wherein the passband has a full width at half maximum transmittance that is less thanabout 600 nm. The refrigeration system is adapted to cool therefrigerated portion of the infrared camera system. The portablechemical leak inspection system also includes a battery, a frame, ashoulder-rest portion, and a handle. The battery is electrically coupledto the infrared camera system, the infrared camera being adapted to bepowered by the battery during use of the chemical leak inspectionsystem. The frame is attached to the infrared camera system. Theshoulder-rest portion extends from the frame. And, the handle extendsfrom the frame.

In accordance with still another aspect of the present invention, aportable passive infrared camera system adapted to provide a focusedvisual image of a chemical emanating from a component having thechemical therein, is provided. The infrared camera system includes alens, a Dewar container, and a refrigeration system. The Dewar containerdefines a refrigerated portion therein. The refrigerated portionincludes therein an infrared sensor device having an array of sensorsadapted to receive an infrared image from the lens and adapted togenerate electrical signals corresponding to the infrared image, and anoptical bandpass filter located along an optical path between the lensand the infrared sensor device, wherein a pass band for the opticalbandpass filter is located between about 3100 nm and about 3600 nm, andwherein the pass band has a full width at half maximum transmittancethat is less than about 600 nm. The refrigeration system is adapted tocool the refrigerated portion.

In accordance with a further aspect of the present invention, a portablepassive infrared camera system adapted to provide a focused visual imageof a chemical emanating from a component having the chemical therein, isprovided. The infrared camera system includes a lens, a Dewar container,and a refrigeration system. The Dewar container defines a refrigeratedportion therein. In this case, the refrigerated portion includes thereinan infrared sensor device having an array of sensors adapted to receivean infrared image from the lens and adapted to generate electricalsignals corresponding to the infrared image, and an optical bandpassfilter located along an optical path between the lens and the infraredsensor device, wherein a pass band for the optical bandpass filter islocated between about 3200 nm and about 3500 nm, wherein the pass bandhas a full width at half maximum transmittance that is less than about80 nm, and wherein the pass band has a center wavelength located betweenabout 3320 nm and about 3440 nm. The refrigeration system is adapted tocool the refrigerated portion.

Although embodiments of the present invention and at least some of itsadvantages have been described in detail, it should be understood thatvarious changes, substitutions, and alterations can be made hereinwithout departing from the spirit and scope of the invention as definedby the appended claims. Moreover, the scope of the present applicationis not intended to be limited to the particular embodiments of theprocess, machine, manufacture, composition of matter, means, methods,and steps described in the specification. As one of ordinary skill inthe art will readily appreciate from the disclosure of the presentinvention, processes, machines, manufacture, compositions of matter,means, methods, or steps, presently existing or later to be developed,that perform substantially the same function or achieve substantiallythe same result as the corresponding embodiments described herein may beutilized according to the present invention. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

What is claimed is:
 1. A system for producing a visible image of a leakof any one or more chemicals of a group of chemicals, the leak emanatingfrom a component, including: a passive infrared camera system including:a lens assembly including a lens; a refrigerated portion including aninterior; an infrared sensor device located in the interior of therefrigerated portion; a single filter configuration located in theinterior of the refrigerated portion and including an optical bandpassfilter fixed along an optical path between the lens assembly and theinfrared sensor device; a refrigeration system that can cool theinterior of the refrigerated portion; wherein at least part of the passband for the single filter configuration is within an absorption bandfor each of the chemicals; and wherein the aggregate pass band for thesingle filter configuration is at least about 100 nm; and a processorthat can process a signal representing the filtered infrared imagecaptured by the infrared sensor device to produce a visible image of thechemical emanating from the component under variable ambient conditionsof the area around the leak.
 2. The system of claim 1, further includinga recording device that can record the visible image of the leakingchemical.
 3. The system of claim 2, wherein the recorded visible imagecan be viewed at a time other than when recorded.
 4. The system of claim2, wherein the recording device can record the visible image along withinspection information about the image selected from a group consistingof inspection location name, inspection location address, componentname, component identification information, global positioningcoordinates, a date, a time of day, an inspector's name, an inspectioncompany's name, one or more camera system setting values, andcombinations thereof.
 5. The system claim 2, further including a voicerecorder that can record voice notes along with the image.
 6. The systemof claim 1, wherein the passive infrared camera system further includesa display screen that can display the visible image of the leakingchemical.
 7. The system of claim 1, wherein the passive infrared camerasystem is powered by a battery and is portable.
 8. The system of claim1, wherein the passive infrared camera system lens assembly includesmore than one lens.
 9. The system of claim 1, wherein the passiveinfrared camera system lens assembly is removable.
 10. The system ofclaim 1, wherein the refrigerated portion is defined by a Dewarcontainer.
 11. The system of claim 1, wherein the refrigeration systemincludes a closed-cycle Stirling cryocooler.
 12. The system of claim 1,wherein the refrigeration system can cool the interior of therefrigerated section to a temperature below about 100 K.
 13. The systemof claim 1, wherein the processor can process the filtered infraredimage captured by the infrared sensor device to produce a visible imageof more than one chemical.
 14. The system of claim 1, wherein theinfrared sensor device captures multiple images and the processor canprocess the multiple images to produce a visible video of the leak. 15.The system of claim 1, wherein, in use, the infrared sensor devicereceives a filtered infrared image from the single filter configurationand converts the filtered image to an electrical signal representing thefiltered infrared image.
 16. The system of claim 1, wherein theprocessor is part of the passive infrared camera system.
 17. The systemof claim 1, wherein the processor is separate from the passive infraredcamera system.
 18. The system of claim 1, wherein the image can beprocessed in real time.
 19. The system of claim 1, further including atransmitter that can transmit the visible image to a location remotefrom the passive infrared camera system.
 20. The system of claim 18,wherein the transmitter can transmit the image using at least one of acable, a wire, a wireless communication device, a network connection,the Internet, or combinations thereof.
 21. The system of claim 1,wherein the any one or more chemicals includes one or more substancesselected from the group consisting of refrigerant; fuel; water vapor;methane; ethane; propane; butane; hexane; ethylene; propylene; o-xylene;toluene; benzene; acetylene; alcohol; ethanol; methanol; xylene;benzene; formaldehyde; 1,2 butadiene; 1,3 butadiene; butadiene; acetone;gasoline; diesel fuel; petroleum; petrochemicals; petroleum by-product;volatile organic compound; volatile inorganic compound; crude oilproducts; crude oil by-products; a hydrocarbon; and compounds andcombinations thereof.
 22. The system of claim 1, wherein the filterconfiguration includes more than one filter.
 23. The system of claim 1,wherein the aggregate pass band for the single filter configuration isat least about 200 nm.
 24. The system of claim 1, wherein the pass bandfor the filter configuration has a center wavelength located betweenabout 3375 nm and about 3385 nm.
 25. The system of claim 1, wherein thepass band for the filter configuration has a center wavelength locatedbetween about 3340 nm and about 3440 nm.
 26. The system of claim 1,wherein the pass band for the filter configuration has a centerwavelength located between about 3360 nm and about 3380 nm.
 27. Thesystem of claim 1, wherein the pass band for the filter configuration islocated between about 2900 nm and about 3200 nm.
 28. The system of claim1, wherein the pass band for the filter configuration is located betweenabout 3100 nm and about 3500 nm.
 29. The system of claim 1, wherein thepass band for the filter configuration is located between about 3100 nmand about 3500 nm.
 30. The system of claim 1, wherein the pass band forthe filter configuration is located between about 3200 nm and about 3500nm.
 31. The system of claim 1, wherein the pass band for the filterconfiguration is located between about 3300 nm and about 3500 nm. 32.The system of claim 1, wherein the pass band for the filterconfiguration is located between about 3200 nm and about 3400 nm. 33.The system of claim 1, wherein the pass band for the filterconfiguration is located between about 9000 nm and about 12000 nm. 34.The system of claim 1, wherein the pass band for the filterconfiguration is located between about 10400 and 10700 nm.
 35. Thesystem of claim 1, wherein the pass band for the filter configuration islocated between about 10000 nm and about 11500 nm.
 36. The system ofclaim 1, wherein the pass band for the filter configuration is locatedbetween about 10500 nm and about 10600 nm.
 37. The system of claim 1,wherein the pass band for the filter configuration has a full width athalf maximum transmittance that is less than about 600 nm.
 38. Thesystem of claim 1, wherein the pass band for the filter configurationhas a full width at half maximum transmittance that is less than about400 nm.
 39. The system of claim 1, wherein the pass band for the filterconfiguration is located between about 3250 nm and about 3510 nm with afull width at half maximum less than about 250 nm.
 40. The system ofclaim 1, wherein the pass band for the filter configuration is locatedbetween about 3200 nm and about 3580 nm with a full width at halfmaximum less than about 350 nm.
 41. The system of claim 1, wherein thepass band for the filter configuration is located between about 7600 nmand about 7800 nm.
 42. The system of claim 1, wherein the pass band forthe filter configuration is located between about 3200 nm and about 3500nm with a full width at half maximum less than about 300 nm.
 43. Thesystem of claim 1, wherein the pass band for the filter configuration islocated between about 3200 nm and about 3600 nm with a full width athalf maximum less than about 400 nm.
 44. The system of claim 1, whereinthe filter configuration allows a transmittance greater than about 70%at the center wavelength of the pass band.
 45. The system of claim 1,wherein the aggregate pass band for the filter configuration includes afull width at half maximum transmittance that is less than about 600 nm.46. The system of claim 1, wherein the center wavelength of the passband for the filter configuration is within an absorption band for oneof the chemicals.
 47. The system of claim 1, wherein the centerwavelength of the pass band for the filter configuration is outside anabsorption band for one of the chemicals.
 48. The system of claim 1,wherein the absorption band of one of the chemicals includes a peak andthe pass band for the filter configuration is centered at or close tothe peak.
 49. The system of claim 1, wherein the absorption band of oneof the chemicals includes a peak and the pass band for the filterconfiguration is not centered at or close to the peak.
 50. The system ofclaim 1, further including a computer programmed with image recognitionsoftware to analyze the image from the processor.
 51. The system ofclaim 1, wherein the passive infrared camera system is attached to orsupported by a movable vehicle selected from the group consisting of amotorcycle, a car, a truck, a bicycle, a boat, a ship, a personalwatercraft, a rotary wing vehicle, an airplane, a powered paraglider, anultralight aircraft, a powered glider, a glider, a balloon, a blimp, aremotely controlled vehicle, an unmanned aerial vehicle, a satellite,and combinations thereof.
 52. The system of claim 1, wherein the passiveinfrared camera system is non-radiometric.
 53. The system of claim 1,wherein the infrared sensor device includes an Indium Antimonide focalplane array of at least 81,920 sensor elements.
 54. The system of claim1, wherein the passive infrared camera system is attached to apermanently installed mount.
 55. The system of claim 1, furtherincluding more than one passive infrared camera system.
 56. The systemof claim 55, wherein the passive infrared cameras are part of a network.57. The system of claim 1, wherein the optical bandpass filter includesa silicon dioxide substrate.
 58. The system of claim 1, wherein therefrigeration system includes a chamber adapted to retain liquidnitrogen.